1. Field of the Invention
The present invention relates to the technical field of mobile ad-hoc networks and, more particularly to a system using label switching techniques to support QoS in mobile ad-hoc networks and its label distributing and switching method.
2. Description of Related Art
Wireless network architecture can be divided into wireless infrastructure networks and mobile ad-hoc networks (MANETs). In the infrastructure network, access points (APs) are implemented in the terminals of wire-line backbones, and a mobile node (MN) can use the APs to link the wire-line backbones for information communication. However, it is disadvantage that the wireless communication can occur only between an AP and an MN but AP deployment is not widespread. By contrast, the mobile ad-hoc network does not use the wire-line backbones, and corresponding NMs use wireless network interface to communication with one another without AP support. Since the range of wireless signaling is limited for a wireless network interface, the communication between NMs may also require other MN as a relay to forward the messages. Although the wireless infrastructure network is the most widely acceptable mode to construct wireless access network until recently, research reports have predicted that mobile ad-hoc networks will be adopted widely in future networks. Further, multimedia transmissions are demanded increasingly and accordingly the requirements of Quality of Service (QoS) control are going to appear in mobile ad-hoc networks, so that the end-to-end QoS guarantee over a mobile ad-hoc network and the Internet must be provided. However, it is not easy to maintain the fixed routing of a mobile ad-hoc network, due to the network topology is changing while the MNs are moving. Also, it is not easy to offer the QoS guarantee in an unstable routing path. Therefore, the MN responsible of forwarding in the mobile ad-hoc network is expected as a low-speed mover or a half-fixed node moving rarely.
In the future, QoS supporting for the streaming multimedia services can be obtained by the QoS architecture of Differentiated Services (DiffServ). To achieve QoS of DiffServ, most researches have applied Multi-Protocol Label Switch (MPLS), which adds label switching in data link layer to support QoS-related bandwidth reservation and management by data connection-oriented setup.
MPLS provided by IETF (Internet Engineering Task Force) is a new generation of IP switching, which combines label swapping and IP routing to effectively increase the performance of IP routing, extensibility of network layer and convenience of new routing services, and provide the support of QoS control services. As shown in FIG. 1, a complete MPLS network is constructed of plural Differentiated Service (DS) domains. Each DS domain is constructed of plural Label Switching Routers (LSRs) and Label Edge Routers (LERs). An LSR performs label switching for packet with labels. An LER can be an ingress or egress node at the entrance or exit of each DS domain of the MPLS network. When an explicit LSP is going to be constructed among LSRs, the MPLS network could apply Label Distribution Protocol (LDP) to distribute routing and label mapping to a respective LSR along the routing path determined by IP routing algorithm. After a Label Switch Path (LSP) is constructed in the DS domain, a respective LER is responsible to the conversion between IP and label. If the respective LER is an ingress node, it is also responsible to data packet classification and monitoring, connection admission control and interaction to the neighboring DS domains. If the respective LER is an egress node, it is also responsible to the remove the label for the data packets that will be forwarded to an IP network.
The advantages of MPLS protocol are that fast and simple label switching between adjacent routers instead of slow and complicated IP routing globally, and it is able to easily support various QoS. Currently, many significant methods can support QoS control mechanism of DiffServ on wire-line backbones. However, since the mobile ad-hoc networks belong to the broadcast networks, several NMs may share a single radio channel and thus the LSP cannot be distinguished by physical line. As such, MPLS protocol in a mobile ad-hoc network needs MAC address to map labels for routing and thus causes original label distribution and switching inappropriately used in wire-line networks. Unfortunately, there are still no any significantly label allocation and QoS control mechanism been proposed in the mobile ad-hoc network until recently. Therefore, it is desirable to provide an improved system and switching method to mitigate and/or obviate the aforementioned problems.